The present disclosure relates to subject matter contained in Japanese Patent Application No. 2000-020956, filed on Jan. 28, 2000, the disclosure of which is expressly incorporated herein by reference in its entirety.
1. Field of the Invention
The present invention relates to an object display method enabling the display of a reflection image reflected from an environment of a virtual moving object on to the moving object, a computer readable program product and program for displaying the object on a game screen, and a game system using the same.
2. Description of the Related Art
An increasing number of recent video games have been so-called 3D games. In such games, virtual objects called three-dimensional characters and formed by polygons are arranged in a virtual three-dimensional space and an image of the field of vision seen from a predetermined perspective is generated and displayed on the screen. For example, one practice has been to display a reflection image reflected from the surroundings of a moving object such as an automobile or train or a stationary object such as a building on the inner surface of the object superposed on the image representing the object. This technique is called environment reflection mapping or simply reflection mapping.
The most frequently used environment reflection mapping technique is spherical reflection mapping. According to this technique, a reflection image representing the environment of an object is determined corresponding to the inner surface of a sphere centered about the approximate center position of the object. For determining the reflection image portion to be reflected on the surface of the object from the environment, a reflection vector is determined at that surface for a vector extending from a viewpoint determined by the camera position to that surface. Next, the reflection image portion is determined based on the point where the reflection vector reaches the inner surface of the sphere when extending it.
In spherical reflection mapping, no matter what the direction of the reflection vector generated at the surface of the object, it is possible to determine a reflection image portion for that surface. When the object is a moving object, when the viewpoint is stationary, since the vector heading from the viewpoint to the moving object changes along with movement of the object, the reflection image portion reflected on the object changes along with movement of the object. Therefore, the reflection image becomes more realistic.
In video games, there are cases where the moving object is tracked by the camera. In this case, the vector heading from the viewpoint to the moving object does not change much at all, so the reflection vector with respect to that vector also changes. In the above spherical reflection mapping, only a reflection vector is used for determination of the reflection image portion. That is, the sphere for representing the reflection image resulting from the environment is assumed to have an infinitely long radius. Even if the moving object moves, the vector heading from the viewpoint to the moving object does not change. In that state, the reflection image portion on the moving object does not change and so the reflection image lacks realism.
An object of the present invention is to provide an object display method enabling the display of a reflection image changing in accordance with a moving object even when making a viewpoint track the moving object, a computer readable program product and program for displaying an object, and a game system using the same.
According to a first aspect of the present invention, there is provided an object display method for displaying an object from a direction of a viewpoint in a virtual three-dimensional space of a video game, comprising making the viewpoint and an object arranged in a cylinder, on the inner surface of which a reflection image representing the environment is provided, move in accordance with predetermined rules or player operation; judging a partial area of the cylinder linked with a reflection image to be reflected on the object in accordance with the positions of the viewpoint and the object; and displaying the image corresponding to the determined partial area of the cylinder combined with the image of the object.
According to a second aspect of the present invention, there is provided a computer readable computer product storing a program for displaying an object from a viewpoint in a three-dimensional space of a video game, the program making the computer make the viewpoint and an object arranged in a cylinder, on the inner surface of which a reflection image expressing the environment is provided, move in accordance with predetermined rules or player operation; judging a partial area of the cylinder to be linked with a reflection image to be reflected on the object in accordance with the positions of the viewpoint and the object; and displaying the image corresponding to the determined partial area of the cylinder combined with the image of the object.
According to a third aspect of the present invention, there is provided a program for displaying an object from a viewpoint in a three-dimensional space of a video game, the program making a computer make the viewpoint and an object arranged in a cylinder, on the inner surface of which a reflection image expressing the environment is provided, move in accordance with predetermined rules or player operation; judging a partial area of the cylinder to be linked with a reflection image to be reflected on the object in accordance with the positions of the viewpoint and the object; and displaying the image corresponding to the determined partial area of the cylinder combined with the image of the object.
According to a fourth aspect of the present invention, there is provided a video game system comprising a computer readable program product storing a program for displaying an object from a viewpoint in a three-dimensional space of a video game; a computer for executing at least part of a program from the program product; and a display for displaying a video game executed by the computer; the computer reading at least part of a program from the program product, making the viewpoint and an object arranged in a cylinder, on the inner surface of which a reflection image expressing the environment is provided, move in accordance with predetermined rules or player operation; judging a partial area of the cylinder to be linked with a reflection image to be reflected on the object in accordance with the positions of the viewpoint and the object; and displaying the image corresponding to the determined partial area of the cylinder combined with the image of the object on the display.